Vehicle vision system with color correction

ABSTRACT

A vision system for a vehicle includes a color camera disposed at a vehicle and having an exterior rearward field of view. The color camera includes an imaging array of photosensing pixels and at least one color filter disposed at or in front of at least some of the photosensing pixels. An image processor is operable to process image data captured by the color camera. Processing of captured image data by the image processor includes utilization of a color correction algorithm that includes a color correction matrix. The color correction matrix algorithm may utilize a 3×3 color correction matrix. The color correction algorithm may include a color correction matrix algorithm and a histogram algorithm that function to determine a color correction for the captured image data.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a 371 national phase filing of PCTApplication No. PCT/US2012/063520, filed Nov. 5, 2012, which claims thefiling benefit of U.S. provisional application, Ser. No. 61/556,556,filed Nov. 7, 2011, which is hereby incorporated herein by reference inits entirety.

FIELD OF THE INVENTION

The present invention relates to imaging systems or vision systems forvehicles.

BACKGROUND OF THE INVENTION

Use of imaging sensors in vehicle imaging systems is common and known.Examples of such known systems are described in U.S. Pat. Nos.5,949,331; 5,670,935; and/or 5,550,677, which are hereby incorporatedherein by reference in their entireties.

SUMMARY OF THE INVENTION

The present invention provides a vision system or imaging system for avehicle that utilizes one or more cameras to capture images exterior ofthe vehicle, such as rearwardly or sidewardly or forwardly of thevehicle. The camera provides communication/data signals, includingcamera data or image data that may be displayed for viewing by thedriver of the vehicle, and/or that may be processed and may detectobjects or vehicles or light sources or the like responsive to suchimage processing. The image data captured by the color image cameras isprocessed via an algorithmic loop that corrects color variations due tolighting conditions and the like so that the images displayed orprocessed represent the substantially true or corrected color of theimaged objects.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vehicle with a vision system and imagingsensor or camera that provides an exterior field of view in accordancewith the present invention;

FIG. 2 is a Planckian Locus with within the r-g color room;

FIG. 2A is a Planckian Locus with tolerance band within a section r-gcolor room;

FIG. 2B is an example of a pattern of intense light spots appearingwithin a natural image close to the Planckian Locus with tolerance bandwithin a section of the r-g color room, with the color correction matrixalgorithm not executed at that point of time CCM(t₀) (initial status ofCCM);

FIG. 2C is the example of FIG. 2B, showing the pattern of intense lightspots shifted substantially in the g direction by a step within asection of the r-g color room, with the color correction matrixalgorithm executed once: CCM(t₀₊₂);

FIG. 2D is the example of FIGS. 2B and 2C, showing the pattern ofintense light spots shifted another step substantially in the ydirection within a section of the r-g color room, with the colorcorrection matrix algorithm executed twice: CCM(t₀₊₂);

FIG. 2E is the example of FIGS. 2B, 2C and 2D, showing the pattern ofintense light spots shifted finally {CCM(t_(0+n))} into a positionwithin a section of the r-g color room where the majority of intense (soassumingly white) light spots is on or close around to the PlanckianLocus;

FIG. 3 is a schematic showing a chain of devices contributing to animage reprocessing, where the goal is that the resulting output imagerepresents the scene which was present in front of the camera, and inthis case a color checker patch was the source image, illuminated by anilluminant of unknown color;

FIG. 4 shows the sensitivity spectrum of a camera plus its typicallyused infra-red filters (at the IR curve), shown with the sensitivity ofthe blue (at the B curve) and green (at the G curve) pixels towavelengths above the visible red (the R curve) being suppressed;

FIG. 5 shows how an algorithm may generate 3×3 CCM matrix values foreach color temperature value (along the Planckian Locus) offline prioruse, shown with the dotted line enclosing the numerical optimizationloop;

FIG. 6A shows a standard ColorChecker® patch board (in black and white);

FIG. 6B shows a standard ColorChecker® patch board with numeratedpatches (in black and white);

FIG. 6C shows a table of weighting factors of color patch according itsposition as used in the algorithm of FIG. 5;

FIG. 6D shows a table of exemplary weighting factors of color patches asused in the algorithm of FIG. 5;

FIG. 7 is a schematic of a 3×3 correction matrix with exemplary curves Ato I that are polynomial alignments to the points or dots or datapoints;

FIG. 8A is a block diagram of a color correction scheme or process thatutilizes a histogram input;

FIG. 8B is a block diagram of a color correction algorithm scheme orprocess having a loop feedback from the histogram to the colorcorrection matrix (CCM) via a color correction matrix algorithm(CCM-Algorithm) in accordance with the present invention; and

FIG. 9 shows a PID control which may be employed for generating the rvalue and the g value out of the color temperature for choosing the ninecorrective color coefficients out of the polynomials.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depictedtherein, a vehicle 10 includes an imaging system or vision system 12that includes at least one imaging sensor or camera (such as a rearwardfacing imaging sensor or camera 14 a and/or optionally such as aforwardly facing camera 14 b at the front (or at the windshield) of thevehicle, and/or a rearwardly and/or sidewardly facing camera 14 c, 14 bat the sides of the vehicle), which captures images exterior of thevehicle, with the camera or camera having a lens for focusing images ator onto an imaging array or imaging plane of the camera (FIG. 1). Thevision system 12 is operable to process image data captured by at leastone camera (such as, for example, the rearwardly facing camera 14 a) todetect objects, such as objects to the rear of the subject or equippedvehicle during a reversing maneuver, or such as approaching or followingvehicles or vehicles at a side lane adjacent to the subject or equippedvehicle or the like, and/or the system may display images captured bythe camera or cameras (such as at a display screen 16 that is viewableby the driver of the vehicle). The method or system or process of thepresent invention is operable to process image data and correct colorvariations so that a display of the captured color images and/orprocessing of the captured color images uses color data or informationthat is substantially adapted or corrected to the true or correct colorof imaged objects to correct for color variations due to color lightingconditions and the like, as discussed below.

It is known to divide the Planckian Locus (which is a varying of gray ona x-y color room (or known as a CIE or Red-Green-Blue or RGB room or r-groom) emitted from a perfectly black body (with blue-green as x, magentagreen as y)) into sections along the locus which are within a toleranceband above and below the locus (but apart from points which representstrong colors), and to use this for calibrating the white balance (suchas for a printer), such as described in U.S. Pat. No. 5,532,848, whichis hereby incorporated herein by reference in its entirety. It has beenproposed that there is a statistical distribution of colors in thedaylight spectrum (see, for example, Deane B. Judd et al., ‘SpectralDistribution of Typical Daylight as a Function of Correlated ColorTemperature,’ 1964, which is hereby incorporated by reference in itsentirety).

The Planckian Locus or black body locus is the path or locus that thecolor of an incandescent black body would take in a particularchromaticity space as the blackbody temperature changes. The path orlocus goes from a deep red color at low temperatures through orange,yellowish white, white, and finally to bluish white colors at very hightemperatures. A color space is a three-dimensional space with colorsspecified by a respective set of three numbers (for example, either theCIE coordinates X, Y, and Z, or other values such as hue, colorfulness,and luminance), which specify the color and brightness of a particularhomogeneous visual stimulus. A chromaticity is a color projected into atwo-dimensional space that ignores brightness. For example, the standardCIE XYZ color space projects directly to the corresponding chromaticityspace specified by the two chromaticity coordinates known as x and y.This is similar to the coordinates on the r (red-blue) axis and g(green-purple) axis in the r-g-room, resulting in a diagram such asshown in FIG. 2. A color opponent room is the perception basedL*a*b*-color room according: EN ISO 11664-4 L*a*b* expressing the colorreproduction/perception device independent r-g and XYZ equating colorscan be translated from one to another by a*/b* diagrams.

Vehicle vision systems are typically equipped with cameras that areactive in the visible spectrum, or other wavelengths, such as nearinfrared and/or infrared wavelengths. It is a typical difficulty toprovide a color camera image to a display screen or processing system,with the color image having colors that closely correspond to the colorsin nature (the imaged objects' natural colors), and such as picked up bya human eye. It is often difficult for automotive cameras to distinguishwhether an object external of the equipped vehicle appears as a specificcolor because the object may be illuminated by a colored light source(for example, by the headlights of the equipped vehicle or by headlightsof other vehicles or by street lights or by street signage, such asreflections of light incident on street signage or illumination fromstreet signage, and especially so during nighttime driving conditions),or the object may be otherwise dis-colored or colored by itself. Inorder to correct the influences of colored illumination and the like,and thus find a white color reference point in the x-y or r-g room, analgorithm may be used that estimates the color temperature (such as of ablack body within the x-y or r-g color room). An example of such analgorithm is a Bretford algorithm, which delivers a color temperature Bof a scene captured in the color temperature A. The Bretford algorithmdelivers a common solution, and occurs typically online, and thus mayconsume valuable processing power of a camera's or vision system'sprocessor or processors.

Instead of running such a color temperature estimation/predictionalgorithm online, it is more economical (and uses reduced onlinecomputing power) to run particular algorithms offline and to providepre-processed parameters in look up tables for a color correction matrix(CCM) during run time. A CCM is specific to illuminant, camera, display(see FIG. 3) and the spectrum filters (such as shown in FIG. 4). A 3×3color correction matrix has been found to be enough to cover most cases(see FIG. 3). There may always be many input color temperatures, butjust one output point.

To generate the matrix elements for all points, a numerical optimizationalgorithm as like a differential evolutional algorithm may be used. Asan execution example there may be signed matrix coefficient values. Foreach illuminant with a specific spectral energy distribution, a sensorand display optimal CCM can be calculated. This process involvesnumerical non-linear optimization and is computation intensive. Thus, itmay not be executed during run time but may be calculated and tabulatedfor use.

For achieving an advantage compared to linear interpolation between twoneighboring coefficient sets a polynomial of any order is fitted alongthe data or pin points which equate to nine polynomic curves that runthrough all matrix coefficient points of one matrix position (A to Iaccording to the chart of FIG. 7). If the spectral properties betweentwo illuminants change in a continuous way like they do with illuminantson the Planckian Locus, it is possible to extract any color temperaturespecific CCM coefficients out of the polynomials for any CCT (CorrelatedColor Temperature).

Referring to FIG. 5, which shows in detail how such an algorithm maygenerate 3×3 matrix values for each color temperature value (along thePlanckian Locus). Hereby simulated is the process to capture a standardColor Checker® patch board (see FIG. 6A) patch (one by one) captured bythe to be used camera with IR-cut-Filter (having the spectral propertiessuch as like shown in the example of FIG. 4) and illuminated by a D65illuminator of a known MIRED, whereby the color image is color correctedby a simulated CCM and then displayed on a simulated display which hassimulated (non perfect) color reproduction properties. The displayreproduces the color image in a specific L*a*b*value. Each patch of theColor Checker® board (see FIG. 6B) has a certain weight factor (w) (seeFIG. 6C), which characterizes the importance of a patch's color. Theweight factor may have values between 0 and 1 (see FIG. 6D). Thedifferences in L*a*b*value of the patch in front of the camera and thatof the image reproduced (by the display) and weighted becomes added in asum of Error (ΔE). When all 24 patches (n) have been simulated, thechange of the sum of all ΔE is compared. There may be other exitcriteria. Optionally, as soon the Error is not diminishing any more, thefound 3×3 coefficients of the color correction matrix are stored forthat currently simulated color temperature (m) of the illuminant,otherwise the CCM becomes altered (optimized into the direction ofsmaller sum of ΔE) and ΔE resets. After one color temperature pointsmatrix coefficients are found, the algorithm resumes with a followingcolor temperature. In the example of FIG. 5 the successive colortemperature (m) is 50 MIREDs lower.

The exemplary curves A to I of FIG. 7 are such nine polynomial curvesrepresenting a 3×3 Color Correction Matrix Coefficient sets along thePlanckian Locus color temperatures generated by an algorithm as likedescribed above.

In some known color correction algorithms (such as represented in FIG.8A), the algorithm adjusts the color correction matrixes (CCM) at onestep depending on the histogram delivered from the image capturingdevice or camera during run time. During run time, the algorithm of thepresent invention (and such as shown in FIG. 8B) does the correction inan iterative (evolutional) loop. The histogram is used as an input tothe color correction matrix algorithm (CCM algorithm) after beingprocessed/corrected/shifted by the color correction matrix (CCM). Thehistogram thus changes during operation and processing, and thus changesthe input parameter of the CCM over subsequent loops.

In nature there is always the statistical probability that gray pointsare prevalent. An accumulation of points tend to appear near to white.The method or process of the present invention identifies theseprobabilities. The color histogram is computed in r-g color space.

The components of the color space are defined as follows:

$r = \frac{R}{R + G + B}$ $g = \frac{G}{R + G + B}$Where R, G and B are the output of the CCM.

Any pixels that fulfill the following conditions must not be used forcolor histograms:

-   -   equal R, G, B components    -   any R, G, B component larger than 90% full scale.

The nominal output range of the CCM is 0 to 1. In extreme cases theoutput of the CCM can be up 15.

The system or method of the present invention selects or establishessections along the Planckian Locus that are within a tolerance bandabove and below the locus (such as shown in FIG. 2A). Each section orbin is assigned two coefficients, one for “r” error signal generationand one for “g” error signal generation. The error signal is the sum ofall bin counts multiplied with the coefficients divided by the sum ofall bin counts. The coefficients must be writeable. The sections abovethe Locus have a negative sign and the sections below the Locus have apositive in the g value. At about the middle there is the to be desiredD65 gray point. At the right of it the tolerance bins have a negativefor sign and at the left the for sign is positive, A color r and g errorsignal may be generated as like this equation:

${error} = \frac{\sum\limits_{i = 1}^{32}\;{c_{i}{count}_{i}}}{\sum\limits_{i = 1}^{32}\;{count}_{i}}$

-   -   c=error coefficient    -   count=color bin i count

The system or method may assume that only points which are within thetolerance band can potentially have a true color of white. For caseswhere the system is massively tuned into red or blue at start up time,the two wider tolerance bins do capture these points. At that bin thehistograms points majority is (within the tolerance band) that r gcorrection the CCM receives as corrective.

The CCM-algorithm may comprise two independent channels which may bothemploy a PID control for visual pleasing color balancing (see FIG. 9).The PID coefficients may be chosen to cope lack time and to hinderoscillating. Its output defines a (normalized) color temperature value(between 0 and 1) which translates to a (unit-less) color temperaturebetween 0 and 100 according to the exemplary curves in FIG. 7. The loopalgorithm migrates to the center weight of white points (as like shownin an exemplary case in the FIGS. 2B, 2C, 2D and 2E). For example, aside maxima of nearly white points may be tracked, and by the migrationof the correction matrix, the white main maxima comes into the range ofthe locus tolerance band. In later processing or subsequent loops, thiswhite maxima becomes centered properly along the locus (as like shown inabove example FIG. 2E). The correction steps may be chosen in aneffective manner, essential is that the direction is the right one, thismeans the leading sign has to be determined correctly. The algorithm ofthe present invention thus adjusts the correction matrix within both ther dimension and the g dimension. When the white maxima is properlycentered, all (other colored) pixels appear in their true orsubstantially true colors of the imaged objects in the display.

Therefore, the present invention uses color cameras (such as pixelatedimaging arrays using spectral filtering that comprises one or more colorfilters or dyes disposed at or in front of the pixelated photosensors ofthe imaging array) and processes the color image data captured by thecamera to correct for color error or variation in the captured colors,such as may be due to colored lighting or the like, whereby the imagedobjects may be displayed in their true or substantially true colorsand/or image data may be processed in its true or substantially truecolors. The system or method of the present invention utilizes ahysteresis loop that receives an output from a color correction matrixalgorithm and that, after processing the output, generates an outputthat is used as the input to the color correction matrix algorithm, suchthat the data is processed in a color correction loop until the colorsare properly corrected and white colors are properly determined to bealong the Planckian Locus. The system or method of the present inventionalso reduces the memory required to process the image data bypre-calculating or pre-determining typical illumination scenarios, suchthat, when a particular illumination scenario is determined, the systemcan utilize a predetermined polynomial equation to calculate data pointsalong the x-y color curve, thus enhancing the efficiency and reducingthe cost and complexity of the system.

The system may utilize an illuminator or light emitter that emitsillumination in a known color or wavelength or range of wavelengths. Theilluminator or light source or light emitter may comprise a Planckianemitter or illuminator. The illuminator may be part of an exterior lightof the vehicle or may be a separate light source that illuminates thearea within the field of view of the imager or camera.

The imaging sensor or camera that captures the image data for imageprocessing may comprise any suitable camera or sensing device, such as,for example, an array of a plurality of photosensor elements arranged inat least about 640 columns and at least about 480 rows (at least a640×480 imaging array), with a respective lens focusing images ontorespective portions of the array. Preferably, the photosensor arraycomprises a mega-pixel array having at least one million pixels. Thephotosensor array may comprise a plurality of photosensor elementsarranged in a photosensor array having rows and columns. The logic andcontrol circuit of the imaging sensor may function in any known manner,and the image processing and algorithmic processing may comprise anysuitable means for processing the images and/or image data. For example,the vision system and/or processing and/or camera and/or circuitry mayutilize aspects described in U.S. Pat. Nos. 7,005,974; 5,760,962;5,877,897; 5,796,094; 5,949,331; 6,222,447; 6,302,545; 6,396,397;6,498,620; 6,523,964; 6,611,202; 6,201,642; 6,690,268; 6,717,610;6,757,109; 6,802,617; 6,806,452; 6,822,563; 6,891,563; 6,946,978;7,859,565; 5,550,677; 5,670,935; 6,636,258; 7,145,519; 7,161,616;7,230,640; 7,248,283; 7,295,229; 7,301,466; 7,592,928; 7,881,496;7,720,580; 7,038,577; 6,882,287; 5,929,786 and/or 5,786,772, and/or PCTApplication No. PCT/US2010/047256, filed Aug. 31, 2010 and publishedMar. 10, 2011 as International Publication No. WO 2011/028686 and/orInternational Publication No. WO 2010/099416, published Sep. 2, 2010,and/or PCT Application No. PCT/US10/25545, filed Feb. 26, 2010 andpublished Sep. 2, 2010 as International Publication No. WO 2010/099416,and/or PCT Application No. PCT/US2012/048800, filed Jul. 30, 2012,and/or PCT Application No. PCT/US2012/048110, filed Jul. 25, 2012,and/or PCT Application No. PCT/CA2012/000378, filed Apr. 25, 2012,and/or PCT Application No. PCT/US2012/056014, filed Sep. 19, 2012,and/or PCT Application No. PCT/US12/57007, filed Sep. 25, 2012, and/orPCT Application No. PCT/US2012/061548, filed Oct. 24, 2012, and/or PCTApplication No. PCT/US2012/062906, filed Nov. 1, 2012, and/or U.S.patent applications, Ser. No. 13/660,306, filed Oct. 25, 2012; Ser. No.13/653,577, filed Oct. 17, 2012; and/or Ser. No. 13/534,657, filed Jun.27, 2012, and/or U.S. provisional applications, Ser. No. 61/710,924,filed Oct. 8, 2012; Ser. No. 61/696,416, filed Sep. 4, 2012; Ser. No.61/682,995, filed Aug. 14, 2012; Ser. No. 61/682,486, filed Aug. 13,2012; Ser. No. 61/680,883, filed Aug. 8, 2012; Ser. No. 61/678,375,filed Aug. 1, 2012; Ser. No. 61/676,405, filed Jul. 27, 2012; Ser. No.61/666,146, filed Jun. 29, 2012; Ser. No. 61/653,665, filed May 31,2012; Ser. No. 61/653,664, filed May 31, 2012; Ser. No. 61/648,744,filed May 18, 2012; Ser. No. 61/624,507, filed Apr. 16, 2012; Ser. No.61/616,126, filed Mar. 27, 2012; Ser. No. 61/615,410, filed Mar. 26,2012; Ser. No. 61/613,651, filed Mar. 21, 2012; Ser. No. 61/607,229,filed Mar. 6, 2012; Ser. No. 61/605,409, filed Mar. 1, 2012; Ser. No.61/602,878, filed Feb. 24, 2012; Ser. No. 61/602,876, filed Feb. 24,2012; Ser. No. 61/600,205, filed Feb. 17, 2012; Ser. No. 61/588,833,filed Jan. 20, 2012; Ser. No. 61/583,381, filed Jan. 5, 2012; Ser. No.61/579,682, filed Dec. 23, 2011; Ser. No. 61/570,017, filed Dec. 13,2011; Ser. No. 61/568,791, filed Dec. 9, 2011; Ser. No. 61/567,446,filed Dec. 6, 2011; Ser. No. 61/567,150, filed Dec. 6, 2011; Ser. No.61/565,713, filed Dec. 1, 2011; Ser. No. 61/563,965, filed Nov. 28,2011; Ser. No. 61/559,970, filed Nov. 15, 2011; Ser. No. 61/556,556,filed Nov. 7, 2011, which are all hereby incorporated herein byreference in their entireties. The system may communicate with othercommunication systems via any suitable means, such as by utilizingaspects of the systems described in PCT Application No. PCT/US10/038477,filed Jun. 14, 2010, and/or U.S. patent application Ser. No. 13/202,005,filed Aug. 17, 2011, and/or U.S. provisional applications, Ser. No.61/650,667, filed May 23, 2012; Ser. No. 61/579,682, filed Dec. 23,2011; Ser. No. 61/565,713, filed Dec. 1, 2011, which are herebyincorporated herein by reference in their entireties.

The vision system may integrate the front and rear cameras, such as byutilizing aspects of the vision systems described in U.S. provisionalapplications, Ser. No. 61/682,486, filed Aug. 13, 2012; and Ser. No.61/648,744, filed May 18, 2012, which are hereby incorporated herein byreference in their entireties. The image processor may comprise an EyeQ2or EyeQ3 image processing chip available from Mobileye VisionTechnologies Ltd. of Jerusalem, Israel, and may include object detectionsoftware (such as the types described in U.S. Pat. Nos. 7,855,755;7,720,580; and/or 7,038,577, which are hereby incorporated herein byreference in their entireties), and may analyze image data to detectvehicles and/or other objects.

The imaging device and control and image processor and any associatedillumination source, if applicable, may comprise any suitablecomponents, and may utilize aspects of the cameras and vision systemsdescribed in U.S. Pat. Nos. 5,550,677; 5,877,897; 6,498,620; 5,670,935;5,796,094; 6,396,397; 6,806,452; 6,690,268; 7,005,974; 7,123,168;7,004,606; 6,946,978; 7,038,577; 6,353,392; 6,320,176; 6,313,454; and6,824,281, and/or International Publication No. WO 2010/099416,published Sep. 2, 2010, and/or PCT Application No. PCT/US10/47256, filedAug. 31, 2010, and/or U.S. patent application Ser. No. 12/508,840, filedJul. 24, 2009, and published Jan. 28, 2010 as U.S. Pat. Publication No.US 2010-0020170, and/or PCT Application No. PCT/US2012/048110, filedJul. 25, 2012, and/or U.S. patent application Ser. No. 13/534,657, filedJun. 27, 2012, which are all hereby incorporated herein by reference intheir entireties. The camera or cameras may comprise any suitablecameras or imaging sensors or camera modules, and may utilize aspects ofthe cameras or sensors described in U.S. patent applications, Ser. No.12/091,359, filed Apr. 24, 2008 and published Oct. 1, 2009 as U.S.Publication No. US-2009-0244361; and/or Ser. No. 13/260,400, filed Sep.26, 2011, and/or U.S. Pat. Nos. 7,965,336 and/or 7,480,149, which arehereby incorporated herein by reference in their entireties. The imagingarray sensor may comprise any suitable sensor, and may utilize variousimaging sensors or imaging array sensors or cameras or the like, such asa CMOS imaging array sensor, a CCD sensor or other sensors or the like,such as the types described in U.S. Pat. Nos. 5,550,677; 5,670,935;5,760,962; 5,715,093; 5,877,897; 6,922,292; 6,757,109; 6,717,610;6,590,719; 6,201,642; 6,498,620; 5,796,094; 6,097,023; 6,320,176;6,559,435; 6,831,261; 6,806,452; 6,396,397; 6,822,563; 6,946,978;7,339,149; 7,038,577; 7,004,606; and/or 7,720,580, and/or U.S. patentapplication Ser. No. 10/534,632, filed May 11, 2005, now U.S. Pat. No.7,965,336; and/or PCT Application No. PCT/US2008/076022, filed Sep. 11,2008 and published Mar. 19, 2009 as International Publication No.WO/2009/036176, and/or PCT Application No. PCT/US2008/078700, filed Oct.3, 2008 and published Apr. 9, 2009 as International Publication No.WO/2009/046268, which are all hereby incorporated herein by reference intheir entireties.

The camera module and circuit chip or board and imaging sensor may beimplemented and operated in connection with various vehicularvision-based systems, and/or may be operable utilizing the principles ofsuch other vehicular systems, such as a vehicle headlamp control system,such as the type disclosed in U.S. Pat. Nos. 5,796,094; 6,097,023;6,320,176; 6,559,435; 6,831,261; 7,004,606; 7,339,149; and/or 7,526,103,which are all hereby incorporated herein by reference in theirentireties, a rain sensor, such as the types disclosed in commonlyassigned U.S. Pat. Nos. 6,353,392; 6,313,454; 6,320,176; and/or7,480,149, which are hereby incorporated herein by reference in theirentireties, a vehicle vision system, such as a forwardly, sidewardly orrearwardly directed vehicle vision system utilizing principles disclosedin U.S. Pat. Nos. 5,550,677; 5,670,935; 5,760,962; 5,877,897; 5,949,331;6,222,447; 6,302,545; 6,396,397; 6,498,620; 6,523,964; 6,611,202;6,201,642; 6,690,268; 6,717,610; 6,757,109; 6,802,617; 6,806,452;6,822,563; 6,891,563; 6,946,978; and/or 7,859,565, which are all herebyincorporated herein by reference in their entireties, a trailer hitchingaid or tow check system, such as the type disclosed in U.S. Pat. No.7,005,974, which is hereby incorporated herein by reference in itsentirety, a reverse or sideward imaging system, such as for a lanechange assistance system or lane departure warning system or for a blindspot or object detection system, such as imaging or detection systems ofthe types disclosed in U.S. Pat. Nos. 7,720,580; 7,038,577; 5,929,786and/or 5,786,772, and/or U.S. pat. applications, Ser. No. 11/239,980,filed Sep. 30, 2005, now U.S. Pat. No. 7,881,496, and/or U.S.provisional applications, Ser. No. 60/628,709, filed Nov. 17, 2004; Ser.No. 60/614,644, filed Sep. 30, 2004; Ser. No. 60/618,686, filed Oct. 14,2004; Ser. No. 60/638,687, filed Dec. 23, 2004, which are herebyincorporated herein by reference in their entireties, a video device forinternal cabin surveillance and/or video telephone function, such asdisclosed in U.S. Pat. Nos. 5,760,962; 5,877,897; 6,690,268; and/or7,370,983, and/or U.S. patent application Ser. No. 10/538,724, filedJun. 13, 2005 and published Mar. 9, 2006 as U.S. Publication No.US-2006-0050018, which are hereby incorporated herein by reference intheir entireties, a traffic sign recognition system, a system fordetermining a distance to a leading or trailing vehicle or object, suchas a system utilizing the principles disclosed in U.S. Pat. Nos.6,396,397 and/or 7,123,168, which are hereby incorporated herein byreference in their entireties, and/or the like.

Optionally, the circuit board or chip may include circuitry for theimaging array sensor and or other electronic accessories or features,such as by utilizing compass-on-a-chip or EC driver-on-a-chip technologyand aspects such as described in U.S. Pat. No. 7,255,451 and/or U.S.Pat. No. 7,480,149; and/or U.S. patent applications, Ser. No.11/226,628, filed Sep. 14, 2005 and published Mar. 23, 2006 as U.S.Publication No. US-2006-0061008, and/or Ser. No. 12/578,732, filed Oct.14, 2009, which are hereby incorporated herein by reference in theirentireties.

Optionally, the vision system may include a display for displayingimages captured by one or more of the imaging sensors for viewing by thedriver of the vehicle while the driver is normally operating thevehicle. Optionally, for example, the vision system may include a videodisplay device disposed at or in the interior rearview mirror assemblyof the vehicle, such as by utilizing aspects of the video mirror displaysystems described in U.S. Pat. No. 6,690,268 and/or U.S. patentapplication Ser. No. 13/333,337, filed Dec. 21, 2011, which are herebyincorporated herein by reference in their entireties. The video mirrordisplay may comprise any suitable devices and systems and optionally mayutilize aspects of the compass display systems described in U.S. Pat.Nos. 7,370,983; 7,329,013; 7,308,341; 7,289,037; 7,249,860; 7,004,593;4,546,551; 5,699,044; 4,953,305; 5,576,687; 5,632,092; 5,677,851;5,708,410; 5,737,226; 5,802,727; 5,878,370; 6,087,953; 6,173,508;6,222,460; 6,513,252; and/or 6,642,851, and/or European patentapplication, published Oct. 11, 2000 under Publication No. EP 0 1043566,and/or U.S. patent application Ser. No. 11/226,628, filed Sep. 14, 2005and published Mar. 23, 2006 as U.S. Publication No. US-2006-0061008,which are all hereby incorporated herein by reference in theirentireties. Optionally, the video mirror display screen or device may beoperable to display images captured by a rearward viewing camera of thevehicle during a reversing maneuver of the vehicle (such as responsiveto the vehicle gear actuator being placed in a reverse gear position orthe like) to assist the driver in backing up the vehicle, and optionallymay be operable to display the compass heading or directional headingcharacter or icon when the vehicle is not undertaking a reversingmaneuver, such as when the vehicle is being driven in a forwarddirection along a road (such as by utilizing aspects of the displaysystem described in PCT Application No. PCT/US2011/056295, filed Oct.14, 2011 and published Apr. 19, 2012 as International Publication No. WO2012/051500, which is hereby incorporated herein by reference in itsentirety).

Optionally, the vision system (utilizing the forward facing camera and arearward facing camera and other cameras disposed at the vehicle withexterior fields of view) may be part of or may provide a display of atop-down view or birds-eye view system of the vehicle or a surround viewat the vehicle, such as by utilizing aspects of the vision systemsdescribed in PCT Application No. PCT/US10/25545, filed Feb. 26, 2010 andpublished on Sep. 2, 2010 as International Publication No. WO2010/099416, and/or PCT Application No. PCT/US10/47256, filed Aug. 31,2010 and published Mar. 10, 2011 as International Publication No. WO2011/028686, and/or PCT Application No. PCT/US2011/062834, filed Dec. 1,2011 and published Jun. 7, 2012 as International Publication No.WO2012/075250, and/or PCT Application No. PCT/US2012/048993, filed Jul.31, 2012, and/or PCT Application No. PCT/US11/62755, filed Dec. 1, 2011and published Jun. 7, 2012 as International Publication No. WO2012-075250, and/or PCT Application No. PCT/US2012/048993, filed Jul.31, 2012, and/or PCT Application No. PCT/CA2012/000378, filed Apr. 25,2012, and/or U.S. patent application Ser. No. 13/333,337, filed Dec. 21,2011, and/or U.S. provisional applications, Ser. No. 61/615,410, filedMar. 26, 2012; Ser. No. 61/588,833, filed Jan. 20, 2012; Ser. No.61/570,017, filed Dec. 13, 2011; Ser. No. 61/568,791, filed Dec. 9,2011; and/or Ser. No. 61/559,970, filed Nov. 15, 2011, which are herebyincorporated herein by reference in their entireties.

Optionally, the video mirror display may be disposed rearward of andbehind the reflective element assembly and may comprise a display suchas the types disclosed in U.S. Pat. Nos. 5,530,240; 6,329,925;7,855,755; 7,626,749; 7,581,859; 7,446,650; 7,370,983; 7,338,177;7,274,501; 7,255,451; 7,195,381; 7,184,190; 5,668,663; 5,724,187 and/or6,690,268, and/or in U.S. patent applications, Ser. No. 11/226,628,filed Sep. 14, 2005 and published Mar. 23, 2006 as U.S. Publication No.US-2006-0061008; and/or Ser. No. 10/538,724, filed Jun. 13, 2005 andpublished Mar. 9, 2006 as U.S. Publication No. US-2006-0050018, whichare all hereby incorporated herein by reference in their entireties. Thedisplay is viewable through the reflective element when the display isactivated to display information. The display element may be any type ofdisplay element, such as a vacuum fluorescent (VF) display element, alight emitting diode (LED) display element, such as an organic lightemitting diode (OLED) or an inorganic light emitting diode, anelectroluminescent (EL) display element, a liquid crystal display (LCD)element, a video screen display element or backlit thin film transistor(TFT) display element or the like, and may be operable to displayvarious information (as discrete characters, icons or the like, or in amulti-pixel manner) to the driver of the vehicle, such as passenger sideinflatable restraint (PSIR) information, tire pressure status, and/orthe like. The mirror assembly and/or display may utilize aspectsdescribed in U.S. Pat. Nos. 7,184,190; 7,255,451; 7,446,924 and/or7,338,177, which are all hereby incorporated herein by reference intheir entireties. The thicknesses and materials of the coatings on thesubstrates of the reflective element may be selected to provide adesired color or tint to the mirror reflective element, such as a bluecolored reflector, such as is known in the art and such as described inU.S. Pat. Nos. 5,910,854; 6,420,036; and/or 7,274,501, which are herebyincorporated herein by reference in their entireties.

Optionally, the display or displays and any associated user inputs maybe associated with various accessories or systems, such as, for example,a tire pressure monitoring system or a passenger air bag status or agarage door opening system or a telematics system or any other accessoryor system of the mirror assembly or of the vehicle or of an accessorymodule or console of the vehicle, such as an accessory module or consoleof the types described in U.S. Pat. Nos. 7,289,037; 6,877,888;6,824,281; 6,690,268; 6,672,744; 6,386,742; and 6,124,886, and/or U.S.patent application Ser. No. 10/538,724, filed Jun. 13, 2005 andpublished Mar. 9, 2006 as U.S. Publication No. US-2006-0050018, whichare hereby incorporated herein by reference in their entireties.

Changes and modifications to the specifically described embodiments maybe carried out without departing from the principles of the presentinvention, which is intended to be limited only by the scope of theappended claims as interpreted according to the principles of patentlaw.

The invention claimed is:
 1. A vision system for a vehicle, said visionsystem comprising: a color camera disposed at a vehicle and having afield of view exterior of the vehicle, wherein said color cameracomprises an imaging array having a plurality of photosensing pixels andat least one color filter disposed in front of at least some of saidphotosensing pixels; an image processor operable to process image datacaptured by said color camera, wherein processing of captured image databy said image processor comprises utilization of a color correctionalgorithm that includes a color correction matrix; wherein said colorcorrection algorithm comprises a color correction matrix algorithm and ahistogram algorithm to determine a color correction for the capturedimage data; and wherein an output of said color correction matrixalgorithm is used as an input to said histogram algorithm and an outputof said histogram algorithm is used as an input to said color correctionmatrix algorithm.
 2. The vision system of claim 1, wherein said colorcorrection matrix algorithm and said histogram algorithm are repeateduntil a desired level of color correction is determined.
 3. The visionsystem of claim 1, wherein said vision system includes a light sourcethat comprises a Planckian emitter.
 4. The vision system of claim 3,wherein said color correction matrix algorithm and said histogramalgorithm repeatedly operate to migrate a plurality of data pointsrepresentative of white points through a color room towards a centerline of white points along a Planckian locus.
 5. The vision system ofclaim 1, wherein said image processor includes polynomial equationsrepresentative of light plots in white illuminated illuminationscenarios, and wherein said image processor, responsive to adetermination that captured image data is representative of a typicalillumination scenario, uses a corresponding polynomial equation todetermine a desired point along a polynomial equation without having tointerpolate between data points.
 6. The vision system of claim 1,wherein said color correction matrix algorithm utilizes a 3×3 colorcorrection matrix.
 7. The vision system of claim 1, wherein said outputof said color correction matrix algorithm used as said input to saidhistogram algorithm and said output of said histogram used as said inputto said color correction matrix algorithm comprise a closed image datacolor control loop algorithm.
 8. The vision system of claim 7, whereinsaid closed image data color control loop algorithm is repeatedlyapplied until a desired level of color correction is determined.
 9. Thevision system of claim 8, wherein said closed image data color controlloop algorithm operates to migrate the plurality of data pointaccumulations representative of white points through the color roomtowards the center line of white points along the Planckian locus. 10.The vision system of claim 1, wherein said color camera is disposed at arear portion of the vehicle and has a field of view rearward of thevehicle.
 11. A vision system for a vehicle, said vision systemcomprising: a color camera disposed at a vehicle and having a field ofview exterior of the vehicle, wherein said color camera comprises animaging array having a plurality of photosensing pixels and at least onecolor filter disposed in front of at least some of said photosensingpixels; an image processor operable to process image data captured bysaid color camera, wherein processing of captured image data by saidimage processor comprises utilization of a color correction algorithmthat includes a color correction matrix; wherein said color correctionalgorithm comprises a color correction matrix algorithm and a histogramalgorithm to determine a color correction for the captured image data;wherein said vision system includes a light source that comprises aPlanckian emitter; wherein said color correction matrix algorithm andsaid histogram algorithm repeatedly operate to migrate a plurality ofdata points representative of white points through a color room towardsa center line of white points along a Planckian locus; and wherein saidhistogram algorithm does not use said data points when an RGB componentof said data points exceeds a threshold fraction of full scale.
 12. Thevision system of claim 11, wherein the threshold fraction of full scaleof said RGB component is about ninety percent.
 13. A vision system for avehicle, said vision system comprising: a color camera disposed at avehicle and having a field of view exterior of the vehicle, wherein saidcolor camera comprises an imaging array having a plurality ofphotosensing pixels and at least one color filter disposed in front ofat least some of said photosensing pixels; an image processor operableto process image data captured by said color camera, wherein processingof captured image data by said image processor comprises utilization ofa color correction algorithm that includes a color correction matrix;wherein said color correction algorithm comprises a color correctionmatrix algorithm and a histogram algorithm to determine a colorcorrection for the captured image data; wherein said vision systemincludes a light source that comprises a Planckian emitter; wherein saidcolor correction matrix algorithm and said histogram algorithmrepeatedly operate to migrate a plurality of data points representativeof white points through a color room towards a center line of whitepoints along a Planckian locus; and wherein said histogram algorithmdoes not use said data points when the RGB components of said datapoints are substantially similar.
 14. A vision system for a vehicle,said vision system comprising: a color camera disposed at a vehicle andhaving a field of view exterior of the vehicle, wherein said colorcamera comprises an imaging array having a plurality of photosensingpixels and at least one color filter disposed in front of at least someof said photosensing pixels; an image processor operable to processimage data captured by said color camera, wherein processing of capturedimage data by said image processor comprises utilization of a colorcorrection algorithm that includes a color correction matrix; whereinsaid color correction algorithm comprises a color correction matrixalgorithm and a histogram algorithm to determine a color correction forthe captured image data; wherein an output of said color correctionmatrix algorithm is used as an input to said histogram algorithm and anoutput of said histogram algorithm is used as an input to said colorcorrection matrix algorithm; and wherein said color correction matrixalgorithm and said histogram algorithm are repeatedly applied until adesired level of color correction is determined.
 15. The vision systemof claim 14, wherein said histogram algorithm does not use said pointswhen an RGB component of said points exceeds a threshold fraction offull scale.
 16. The vision system of claim 14, wherein said colorcorrection matrix algorithm and said histogram algorithm repeatedlyoperate to migrate a plurality of data points representative of whitepoints through a color room towards a center line of white points alonga Planckian locus.
 17. A vision system for a vehicle, said vision systemcomprising: a color camera disposed at a vehicle and having a field ofview exterior and rearward of the vehicle, wherein said color cameracomprises an imaging array having a plurality of photosensing pixels andat least one color filter disposed in front of at least some of saidphotosensing pixels; an image processor operable to process image datacaptured by said color camera, wherein processing of captured image databy said image processor comprises utilization of a color correctionalgorithm that includes a color correction matrix; wherein said colorcorrection algorithm comprises a color correction matrix algorithm and ahistogram algorithm to determine a color correction for the capturedimage data; wherein said vision system includes a light source thatcomprises a Planckian emitter; wherein said color correction matrixalgorithm and said histogram algorithm operate to migrate a plurality ofdata points representative of white points towards white points along aPlanckian locus; and wherein at least one of (i) said histogramalgorithm does not use said data points when an RGB component of saiddata points exceeds a threshold fraction of full scale and (ii) saidhistogram algorithm does not use said data points when the RGBcomponents of said data points are substantially equal.
 18. The visionsystem of claim 17, wherein said color correction matrix algorithm andsaid histogram algorithm are repeatedly applied until a desired level ofcolor correction is determined.